Apparatus for high temperature treatment of rectilinear-generatrix surfaces of nonconductive products

ABSTRACT

Disclosed is an apparatus for high temperature treatment of rectilinear-generatrix surfaces of nonconductive products. The apparatus comprises an anode arranged opposite to a cathode to provide an arc gap therebetween for striking an arc discharge. The apparatus is further provided with a product feeding device to move the product a desired distance from the axis of the arc. The cathode is held securely in place, while the anode is positioned, integrally with the fixed cathode, to maintain a fixed position of the arc axis within the arc gap exceeding the length of the generatrix of the surface being treated. The feeding device is designed so as to provide the movement of the products in a plane extending normally to the axis of the arc when the generatrix of the surface being treated is parallel to the axis of the arc.

FIELD OF THE INVENTION

The present invention relates to the art of high temperature surfacetreatment of products made from nonconductive materials, in particular,from artificial stone materials, such as ceramics, silicate, concrete.More particularly, the invention relates to apparatus for hightemperature treatment of rectilinear-generatrix surfaces ofnonconductive products, e.g. for treating flat, cylindrical, tapered andthe like surfaces.

The invention can most advantageously be used for surface fusion ofbuilding products made from artificial stone materials to provide afused layer having a glazed structure and exhibiting protective anddecorative properties.

DESCRIPTION OF THE PRIOR ART

Known in the prior art is a high temperature surface treatment apparatusadapted for treating products made from nonconductive materials (cf.USSR Inventor's Certificate No. 172,663), which apparatus comprises anoxyacetylene burner used as a high temperature source and a burnertransfer device adapted for relative movement of the burner and theproduct being treated at a desired distance between the product surfaceand the burner nozzle. During the treating process, the burner flame issubstantially directed at right angles to the surface being treated,and, therefore, the effective heat transfer occurs within the limits ofthe flame spot on the product surface. Moreover, the burner is arrangedto move to and fro over the surface to be treated, resulting in thesurface layer thus treated possessing heterogeneous properties in atransverse direction with respect to the path of movement of the burner,which in turn results in visible boundaries between the treated paths,i.e. in a so called "stripped" structure of the surface layer. Moreover,said apparatus suffers from poor efficiency due to a small area of heatcontact between the flame and the surface and due to a relatively lowtemperature of the oxyacetylene flame.

There is also known a high temperature surface treatment apparatus (cf.U.S. Pat. No. 3,584,184) wherein a plasma generation device is used foreffecting a surface treatment of products made from nonconductivematerials and having rectilinear-generatrix surfaces. The plasmagenerator comprises an anode arranged opposite to a cathode to providean arc gap therebetween for striking an arc discharge. The apparatus isfurther provided with a product transfer device enabling the product tobe moved at a desired distance from the arc axis. The anode is shapedlike an elongated box held securely in place and extending along thewhole length of the generatrix of the surface to be treated, while thecathode is operatively associated with a cathode transfer deviceproviding reciprocating movement of the cathode along the length of theanode. In this apparatus, the arc is excited in a transverse plane withrespect to the surface generatrix and is caused to be moved point bypoint along the surface generatrix. The use of the plasma treatment andthe provision of an increased area of heat contact of the plasma arcwith the surface makes it possible to increase the efficiency of saidhigh temperature surface treatment apparatus, as compared to the knownapparatus provided with the oxyacetylene burner.

However, the apparatus in question fails to eliminate the "stripped"structure of the fused surface, resulting from the fact that, during thetreating process, the cathode is caused to be moved repeatedly to andfro over the surface. As a result, said apparatus fails to provide asmooth fused surface and a homogeneous structure of the fused layer.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus forhigh temperature treatment of rectilinear-generatrix surfaces ofnonconductive products, ensuring the production of smooth fused surfacesand the homogeneous structure of the fused surface layer.

Another object of the present invention is to increase the productivityand efficiency of the apparatus for high temperature treatment ofrectilinear-generatrix surfaces of nonconductive products.

With these and other objects in view, there is proposed an apparatus forhigh temperature treatment of rectilinear-generatrix surfaces ofnonconductive products, comprising an anode of a plasma generatorarranged opposite to its cathode to provide an arc gap therebetween, anda product feeding device adapted to move the product a desired distancefrom the axis of the arc. According to the invention, the cathode ismounted in a fixed position, while the anode is positioned, integrallywith the fixed cathode, to maintain a fixed position of the arc axiswithin the arc gap exceeding the length of the generatrix of the surfacebeing treated. The feeding device is designed so as to provide movementof the products in a plane extending normally to the axis of the arcwhen the generatrix of the surface being treated is parallel to the axisof the arc.

The proposed apparatus ensures high temperature treatment of the wholesurface of the product as the product is continuously moved in onedirection, and eliminates the reciprocating movement of the hightemperature source with respect to the surface being treated. As aresult, a smooth fused surface is produced having a homogeneousstructure of the fused layer. Moreover, the high temperature surfacetreatment of the product moving continuously in one direction and thepossibility of eliminating the reciprocating movement of the hightemperature source with respect to the surface being treated increasesthe efficiency of the proposed apparatus.

In one embodiment, the anode takes the form of a hollow rod coaxiallyarranged with the cathode, the anode interior cavity communicating witha suction device, e.g. with a fan. In doing so, the plasma contact spoton the anode is located within the anode, thus enabling the outersurface of the anode to be freely cooled. As a result, the possibilityexists of using low-melting materials for the anode, such as copper.

In order to prevent the plasma jet shorting against the outer surface ofthe anode shaped like a hollow rod, it is advisable that the end face ofthe anode should be provided with a water-cooled flat screenelectrically insulated from the anode and having a central opening equalto and coaxial with the hollow opening provided in the anode.

In another embodiment, the anode coaxially arranged with the cathode isshaped like a pin blown over by a working gas flowing towards thecathode. In this case, it is impossible to provide the effective coolingof the anode, which results in the necessity of using the anodes made ofrefractory materials, such as wolfram. However, the use of the counterflow of gas passing around the electrodes of the plasma generatorresults in an increased concentration of energy of the plasma jet andupgrades the apparatus efficiency.

In still another embodiment, the anode is formed by two parallelcylinders rotated in opposition and having their axes extending normallyto the axis of the arc, the gap provided therebetween being smaller thanthe diameter of the plasma contact spot on the anode. Such an embodimentof the anode reduces the fluctuation of the plasma parameters andimproves the stability of the plasma spatial position.

In order to increase the service life of the anode formed by twocylinders, it is advisable to arrange the cylinders on a movable supportconnected with a support transfer mechanism used to move the support toand fro along the axes of the cylinders.

It is preferable that the feeding device be designed as two similarconveyers arranged symmetrically about the arc axes. This enables theapparatus productivity to be doubled and upgrades the efficiency thereofdue to a more effective use of the plasma energy, i.e. due to theconfinement of the plasma and multiple reflection of the plasma jet fromthe product surfaces being treated.

In order to increase the efficiency of the apparatus with unilateralarrangement of the feeding device with respect to the arc axis, it isdesirable that a water-cooled screen electrically insulated from theanode and cathode be mounted on the opposite side of the arc axis.

BRIEF DESCRIPTION OF THE INVENTION

The foregoing and other objects and advantages of the invention will bebetter understood from the following description taken in conjunctionwith the accompanying drawings illustrating preferred embodiments of theinvention, wherein:

FIG. 1 is a longitudinal sectional view taken along the axis of theplasma generator arc and illustrating an apparatus, according to theinvention, adapted for high temperature surface treatment of a brick;

FIG. 2 is a view of a high temperature surface treatment apparatuswherein the anode is shaped like a pin, according to the invention;

FIG. 3 is a view of a high temperature surface treatment apparatuswherein the anode is formed by two parallel cylinders, according to theinvention;

FIG. 4 is a top view taken in the direction of arrow IV of FIG. 3 andillustrating the anode assembly;

FIG. 5 is a sectional view taken along the axis of the arc andillustrating the apparatus adapted for high temperature surfacetreatment of cylindrical products; and

FIG. 6 is a view of a high temperature surface treatment apparatus withunilateral arrangement of the feeding device, according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the accompanying drawings and initially to FIG. 1, theproposed apparatus for high temperature surface treatment of bricks isadapted to form a fused surface layer on a brick, exhibiting protectiveand decorative properties.

The apparatus comprises a plasma generator (not shown) having an anode 1arranged opposite to its cathode 2 so as to provide an arc gap Htherebetween, wherein an arc having a rectilinear axis 3 is initiated.The apparatus is further provided with a feeding device 4 adapted tomove products 5 at a desired distance from the arc axis 3, the productsurfaces 6 being formed by a rectilinear generatrix 7.

The arc gap H provided between the anode 1 and the cathode 2 exceeds thelength of the generatrix 7 of the brick surface 6 being treated. Thecathode 2 is held securely in place, while the anode is designed tomaintain a fixed position of the arc axis 3.

The anode 1 is made as a hollow copper rod 8 coaxially arranged in avertical plane with the cathode 2 made as a wolfram pin 9.

An interior cavity 10 of the anode rod 8 is in communication with asuction device 11, e.g. with a fan. A governor valve 12 is disposed inthe passage connecting the interior cavity 10 with the fan 11. Formedaround the lower portion of the anode rod 8 is a circular cavity 13communicating with a coolant circulation system (not shown).

A solenoid 14 is concentrically arranged with the circular cavity 13 toproduce a rotating magnetic field with its center extending around theaxis of the anode 1. Attached to the lower end face of the anode rod 8is a flat screen 15 electrically insulated therefrom by means of aninsulating spacer 16. A central opening 17 provided in the screen 15 isequal to and coaxial with the opening of the interior cavity 10 of theanode rod 8. The screen 15 has passages 18 which are in communicationwith the coolant circulation system (not shown).

A chuck collet 19 serves to secure the cathode pin 9 in a sleeve 20 madeof dielectric material and pressed into a housing 21. A nozzle 22 isarranged in the upper portion of the housing 21 and disposed around thetop of the cathode pin 9, which nozzle is provided with a centralopening 23 used to stabilize and confine the plasma jet. Formed betweenthe nozzle 22 and the inner surface of the housing 21 is a circularcavity 24 communicating with the coolant circulation system (not shown).Between the nozzle 22 and the pin 9 there is formed a cavity 25 which isin communication with a source (not shown) of working gas, such asnitrogen.

The feeding device 4 is designed as two rectilinear conveyers 26 adaptedto move the bricks 5 in a plane extending normally to the axis 3 of thearc, when the generatrix 7 of the surface 6 being treated is disposedparallel to the arc axis 3. The conveyors 26 are mounted symmetricallyabout the arc axis 3 and provided with rectilinear projections 27arranged to fix the position of the bricks 5 placed on said conveyers,the projections 27 being arranged along the axes of the conveyers 26 andsymmetrically about the axis 3 of the arc.

The proposed apparatus described hereinabove operates as follows.

D-c voltage is applied to the anode 1 and the cathode 2. In operation,the stream of coolant circulates through the cavities 13 and 24 and thepassages 18 for cooling the anode 1, the cathode 2 and the screen 15.The working gas is fed into the cavity 25 and the exhaust fan 11 is thenenergized to suck the gas out of the interior cavity 10 of the hollowrod 8, whereupon the arc is initiated, the straightness and stability ofthe arc being provided by controlling the gas consumption. The governorvalve 12 is used to control the amount of gas sucked out of the interiorcavity 10 of the hollow rod 8, thus providing a required position of theanode spot in the axial direction.

On attaining steady operating conditions of the apparatus, the conveyers26 are switched on, the bricks 5 being placed on the conveyers 26 sothat the surfaces 6 to be treated are facing each other. The bricks 5are butted up against the projections 27 to provide a fixed position atwhich the generatrices 7 of the brick surfaces 6 are symmetric about thearc axis 3 and parallel therewith. The magnetic field produced by thesolenoid 14 enables the arc contact spot to be moved around the innerperiphery of the cavity 10 of the anode rod 8. The flow of gas suckedout of the interior cavity 10 provides the displacement of the arccontact spot in the axial direction. The screen 15 serves to prevent thearc shorting against the solenoid 14 and other elements of the anode 1and provides additional stabilization of the arc formed in the arc gapbetween the anode 1 and the cathode 2.

The conveyers 26 cause the bricks 5 to move continuously and in the areaof the contact of the surface 6 to be treated with the plasma jet theretakes place an immediate heating of the whole surface 6 along the lengthof the generatrix 7. Thus, the surface fusion of the bricks 5 iseffected in one path of the bricks 5 moving in one direction. As aresult, the fused layer has a homogeneous structure and a flat smoothsurface, which is of particular importance to decorative surfacetreatment of building products. The feeding device formed by twoconveyers 26 enables a pair of products 5 to be simultaneously treated,thus doubling the productivity of the apparatus. Furthermore, in theproposed apparatus, there is provided the confinement of the plasma jet,which results in its stability and in an increased area of heat contactbetween the plasma jet and the surface 6 being treated. The multiplereflection of the plasma jet from the product surfaces 6 provides aneffective convection-radiative heat transfer. All these factors takentogether make it possible to increase the productivity and efficiency ofthe plasma treatment.

In the embodiment shown in FIG. 2, the anode 1 is shaped like a wolframpin 28, the assembling thereof being similar to that of the cathode pin9 shown in FIG. 1. Similar elements are designated by the same referencenumerals in FIGS. 1 and 2. During the treating process, the working gasis supplied into the cavities 25 of the anode assembly 1 and the cathodeassembly 2 for striking an arc discharge therebetween. The arc isconfined passing through the nozzles 22 of the anode 1 and the cathode 2and the arc temperature is 1.5 times higher that the temperature of thearc in the modification shown in FIG. 1. The counter flow of the workinggas increases the heat transfer and, as a result, the efficiency of theapparatus as compared to the modification shown in FIG. 1.

Since the arc is exposed to two oppositely directed flows of the workinggas, at the point of interaction of said flows there is formed an area29 of the arc expansion, the diameter of the arc in said area being2-2.5 times greater than the diameter of the arc outside of said area.Altering the ratio of consumption of the working gas passing through thenozzles 22 of the anode 1 and the cathode 2, it is possible to adjustthe position of the area 29 along the arc axis 3. Moreover, thepossibility exists of finding such a position of the area 29 at whichthe area 29 adjoins one of the edges of the surface 6. In this case, inaddition to the treatment of the surface 6, the possibility exists ofpartly fusing a surface 30 crossing the surface 6, the fused areaextending 6-10 mm from the intersection of the surfaces 30 and 6. Thismay prove to be useful for surface fusion of some types of products.

In the embodiment shown in FIG. 3, the anode 1 is formed by two parallelcylinders 31 made of copper and arranged to provide therebetween a gap32 which is smaller in size than the contact arc spot in said cylinders,similar elements being designated by the same reference numerals inFIGS. 1 and 3. The cylinders 31 are mounted to have their axes extendingnormally to the axis 3 of the arc and are connected with a rotary drive33 used to rotate said cylinders in opposition, in the gap 32 thetangential component of the peripheral speed of the cylinders 31 beingdirected away from the cathode 2. The cylinders 31 and the rotary drive33 are mounted on a movable support 34 (FIG. 4) connected with a supporttransfer mechanism 35 adapted to move the support 34 to and fro alongthe axes of the cylinders 31.

The embodiment of the anode 1 shown in FIG. 3 provides a fixed positionof the arc axis 3 and enables the arc to be brought in active contactwith the surfaces of the cylinders 31 rotated in opposition, thusensuring increased stability of the spatial position of the arc axis 3and reducing the fluctuation of the arc parameters as compared to themodification shown in FIGS. 1 and 2. Moreover, the reciprocatingmovement of the cylinders 31 gives rise to an effective heatdistribution and provides minimum and uniform errosion over the wholesurface of the cylinders 31.

Shown in FIG. 5 is the apparatus adapted for surface treatment of hollowcylindrical products, the elements shown in FIG. 5 and similar to theelements shown in FIG. 1 being designated by the same referencenumerals. In this apparatus, the feeding device 4 is formed by tworotary conveyers 37 arranged symmetrically about the arc axis 3 androtated in a plane extending normally to said axis. The conveyers 37 arebrought into rotation by means of an electric motor (not shown)connected therewith via a reducer 38. Peripherally mounted on theconveyers 37 are mechanisms 39 which are equally spaced and used toposition and to rotate the products 5 about their axes so that thegeneratrix 7 of the surface 6 is parallel with the axis 3 of the arc,the surface 6 being disposed at a required distance from the axis 3.

The mechanism 39 comprises a lower driving cone 40 operativelyassociated with a rotary drive (not shown) via a friction gear 41 and areducer 42, and an upper centering cone 43 fitted onto the end portionof a lever 44 in contact with an eccentric or cam 45 connected with adrive (not shown) and adapted for lifting the lever 44 when removing andmounting the products 5.

In operation of the apparatus shown in FIG. 5, the plasma arc is formedin the same manner as hereinbefore described. Then the products 5 areplaced on the rotary conveyers 37, the products 5 being mounted onrespective lower cones 40 at a maximum distance from the arc axis 3 andthen being fixed by the respective upper centering cone 43. Thenconveyers 37 are energized to replace the products 5 to be treated andto dispose them at a minimum distance from the arc axis 3, whereupon thedrive of the mechanism 39 is energized, the friction gear 41 being usedto establish the required speed of the product 5 to be treated. Thesurface 6 is subjected to high temperature treatment during one completerevolution of the product 5. Coincidentally with the treating process, anew pair of the products 5 to be treated is placed on the conveyers 37.Upon completion of the treatment of one pair of the products 5, thedrive of the mechanism 39 is shut down, while the drive of the conveyers37 is energized to move a new pair of products 5 and to dispose them ata minimum distance from the axis 3 of the arc.

In the embodiment shown in FIG. 6, the feeding device 4 is designed as asingle conveyer 44 used to transfer the products 5 on one side about thearc axis 3, the elements similar to the elements shown in FIG. 1 beingdesignated by the same reference numerals. Mounted on the opposite sideabout the axis 3 is a screen 45 provided with passages 46 incommunication with the coolant circulation system (not shown). Thescreen 45 is electrically insulated from the electrodes of the plasmagenerator and arranged along the axis 3 of the arc and at a distancetherefrom equal to 0.2-0.3 diameter of the arc. In operation, the screen45 serves to provide contact of the plasma arc with the surface 6 andensures multiple reflection of the arc, thus enabling the heat of thearc to be more effectively used when treating the products 5 movingalong one side about the arc axis 3.

While particular embodiments of the invention have been shown anddescribed, various modifications thereof will be apparent to thoseskilled in the art. Thus, the construction of the feeding device may bedifferent from that described above, for example, for treating flatproducts the feeding device may be formed as a carriage connected with acarriage transfer mechanism adapted for reciprocating movement of thecarriage and having a rapid return stroke. When treating cylindricalproducts, the feeding device may be formed as a rectilinear conveyerwith a means for positioning and rotating the product being treated. Itis allowable to arrange the anode and cathode so as to extend the axisof the arc in a horizontal plane. There are also possible various othermodifications of the anode and cathode assemblies. Therefore, variousmodifications may be made in the invention without departing from thespirit and scope of the following claims.

What is claimed is:
 1. An apparatus for high temperature treatment ofrectilinear-generatrix surfaces of nonconductive products, comprising aplasma generator having an anode arranged opposite to a cathode tocreate therebetween an arc gap exceeding the length of a generatrix ofthe surface being treated, said cathode being mounted in a fixedposition, and said anode being mounted integrally with said cathode tomaintain a fixed position of the arc axis within said arc gap; and aproduct feeding device to move said product a desired distance from thearc axis in a plane extending normally to the arc axis when thegeneratrix of the surface being treated is parallel to the arc axis;means for moving an arc contact spot over the surface of said anode;means for displacing said arc contact spot along the arc axis; whereinsaid anode includes a hollow rod having an interior cavity incommunication with a suction device; a water-cooled screen attached tothe end face of said anode and electrically insulated from said anode,said screen having a central opening which is equal to and coaxial withan opening of said interior cavity of said anode.
 2. An apparatus asclaimed in claim 1, wherein said feeding device includes two similarconveyers arranged symmetrically about said arc axis.
 3. An apparatus asclaimed in claim 1, wherein said feeding device is disposed on a firstside of the arc axis; and further comprising a water-cooled screenelectrically insulated from said anode and cathode and disposed on asecond side of said arc axis.
 4. An apparatus for high temperaturetreatment of rectilinear-generatrix surfaces of nonconductive products,comprising a plasma generator having an anode arranged opposite to acathode to create therebetween an arc gap exceeding the length of ageneratrix of the surface being treated, said cathode being mounted in afixed position, and said anode being mounted integrally with saidcathode to maintain a fixed position of the arc axis within said arcgap; and a product feeding device to move said product a desireddistance from the arc axis in a plane extending normally to the arc axiswhen the generatrix of the surface being treated is parallel to the arcaxis; means for moving an arc contact spot over the surface of saidanode; means for displacing said arc contact spot along the arc axis;wherein said anode includes two parallel cylinders rotated in oppositionand having axes extending normally to the arc axis, a gap providedbetween said cylinders being smaller than a diameter of the contactplasma spot on said anode.
 5. An apparatus as claimed in claim 4,wherein said cylinders are mounted on a movable support connected with asupport transfer mechanism for reciprocating movement of said supportalong the axes of said cylinders.
 6. An apparatus as claimed in claim 4,wherein said feeding device includes two similar conveyers arrangedsymmetrically about said arc axis.
 7. An apparatus as claimed in claim4, wherein said feeding device is disposed on a first side of the arcaxis; and further comprising a water-cooled screen electricallyinsulated from said anode and cathode and disposed on a second side ofsaid arc axis.
 8. An apparatus as claimed in claim 5, wherein saidfeeding device is disposed on a first side of the arc axis; and furthercomprising a water-cooled screen electrically insulated from said anodeand cathode and disposed on a second side of said arc axis.
 9. Anapparatus for high temperature treatment of rectilinear-generatrixsurfaces of nonconductive products, comprising a plasma generator havingan anode arranged opposite to a cathode to create therebetween an arcgap exceeding the length of a generatrix of the surface being treated,said cathode being mounted in a fixed position, and said anode beingmounted integrally with said cathode to maintain a fixed position of thearc axis within said arc gap; and a product feeding device to move saidproduct a desired distance from the arc axis in a plane extendingnormally to the arc axis when the generatrix of the surface beingtreated is parallel to the arc axis; means for moving an arc contactspot over the surface of said anode; means for displacing said arccontact spot along the arc axis; wherein said feeding device is disposedon a first side of the arc axis; and, a water-cooled screen electricallyinsulated from said anode and cathode and disposed on a second side ofsaid arc axis.
 10. An apparatus for high temperature treatment ofrectilinear-generatrix surfaces of nonconductive products, comprising aplasma generator having an anode arranged opposite to a cathode tocreate therebetween an arc gap exceeding the length of a generatrix ofthe surface being treated, said cathode being mounted in a fixedposition, and said anode being mounted integrally with said cathode tomaintain a fixed position of the arc axis within said arc gap; and aproduct feeding device to move said product a desired distance from thearc axis in a plane extending normally to the arc axis when thegeneratrix of the surface being treated is parallel to the arc axis;means for moving an arc contact spot over the surface of said anode;means for displacing said arc contact spot along the arc axis; whereinsaid anode includes a rod coaxially arranged with said cathode andwherein said feeding device is disposed on a first side of the arc axis;and, a water-cooled screen electrically insulated from said anode andcathode and disposed on a second side of said arc axis.
 11. An apparatusfor high temperature treatment of rectilinear-generatrix surfaces ofnonconductive products, comprising a plasma generator having an anodearranged opposite to a cathode to create therebetween an arc gapexceeding the length of a generatrix of the surface being treated, saidcathode being mounted in a fixed position, and said anode being mountedintegrally with said cathode to maintain a fixed position of the arcaxis within said arc gap; and a product feeding device to move saidproduct a desired distance from the arc axis in a plane extendingnormally to the arc axis when the generatrix of the surface beingtreated is parallel to the arc axis; means for moving an arc contactspot over the surface of said anode; means for displacing said arccontact spot along the arc axis; wherein said anode includes a hollowrod having an interior cavity in communication with a suction device andwherein said feeding device is disposed on a first side of the arc axis;and, a water-cooled screen electrically insulated from said anode andcathode and disposed on a second side of said arc axis.
 12. An apparatusfor high temperature treatment of rectilinear-generatrix surfaces ofnonconductive products, comprising a plasma generator having an anodearranged opposite to a cathode to create therebetween an arc gapexceeding the length of a generatrix of the surface being treated, saidcathode being mounted in a fixed position, and said anode being mountedintegrally with said cathode to maintain a fixed position of the arcaxis within said arc gap; and a product feeding device to move saidproduct a desired distance from the arc axis in a plane extendingnormally to the arc axis when the generatrix of the surface beingtreated is parallel to the arc axis; means for moving an arc contactspot over the surface of said anode; means for displacing said arccontact spot along the arc axis; wherein said anode includes a rodcoaxially arranged with said cathode, a pin and a nozzle concentricallyarranged with said pin and through which a working gas flows towardssaid cathode; wherein said feeding device is disposed on a first side ofthe arc axis; and, a water-cooled screen electrically insulated fromsaid anode and cathode and disposed on a second side of said arc axis.13. An apparatus for high temperature treatment ofrectilinear-generatrix surfaces of nonconductive products, comprising aplasma generator having an anode arranged opposite to a cathode tocreate therebetween an arc gap exceeding the length of a generatrix ofthe surface being treated, said cathode being mounted in a fixedposition, and said anode being mounted integrally with said cathode tomaintain a fixed position of the arc axis within said arc gap; and aproduct feeding device to move said product a desired distance from thearc axis in a plane extending normally to the arc axis when thegeneratrix of the surface being treated is parallel to the arc axis;means for moving an arc contact spot over the surface of said anode;means for displacing said arc contact spot along the arc axis; whereinsaid means for displacing the arc contact spot along the arc axiscomprises suction means connected to an interior cavity of said anode,and working gas is withdrawn from said cavity of said anode by saidsuction device to effect axial displacement of the arc contact spot. 14.An apparatus as claimed in claim 13, wherein said means for moving saidarc contact spot around the periphery of the anode comprises a solenoidconcentrically arranged with the anode and creating a rotating magneticfield having its center extending around the axis of the anode.